Memory is often incorporated into integrated circuitry. The memory may be used, for example, in computer systems for storing data.
Memory may be fabricated as an array of individual memory cells, with each memory cell being configured to retain or store memory in at least two different selectable states. In a binary system, the storage conditions are considered as either a “0” or a “1”.
Individual memory cells might be volatile, semi-volatile, or nonvolatile. Nonvolatile memory cells can store data for extended periods of time, and many types of nonvolatile memory cells can maintain data storage even in the absence of power. In contrast, volatile memory dissipates and is therefore refreshed/rewritten to maintain data storage.
Integrated circuitry fabrication continues to strive to produce smaller and denser integrated circuits. There is a continuing effort to reduce the number of components in individual devices because such can reduce the size of finished constructions, and can simplify processing. The smallest and simplest memory cell will likely be comprised of two conductive electrodes having a programmable material received between them.
Suitable programmable materials have two or more selectable resistive states to enable storing of information by an individual memory cell. The reading of the cell comprises determination of which of the states the programmable material is in, and the writing of information to the cell comprises placing the programmable material in a predetermined resistive state. Some programmable materials retain a resistive state in the absence of refresh, and thus may be incorporated into nonvolatile memory cells.
Programmable materials that are receiving increasing interest are materials containing multiple discrete layers. Example multi-layer programmable materials are dual-layer materials containing two different oxide layers. Such dual-layer materials may be programmed by moving oxygen species (for instance, oxygen ions) within and between the layers of the materials.
The utilization of multi-layer programmable materials can provide advantages in nonvolatile memory applications. For instance, the multi-layer programmable materials may enable specific memory states to be tailored for particular applications. However, although multi-layer programmable materials show promise for utilization in nonvolatile memory architectures, there remain challenges in incorporating such materials into integrated circuitry.